1. Field of the Invention
The present invention relates to information signal recording apparatus and method, information signal copying system and method, and an information signal recording medium. More particularly, the invention relates to a copy prevention system in which a signal is not lost even in a communication by an analog signal.
2. Description of the Prior Art
There are some methods for copy prevention in a recording system of digital data, for example, a digital VTR (video tape recorder). One of them is a method of inhibiting a copy by adding a copy control signal to digital data. First, a principle of a copy prevention system will be described. FIG. 1 is a diagram showing the principle of the copy prevention system. In FIG. 1, reference numeral 100 denotes a reproducing apparatus; 101 a recording medium for reproduction; 102 a reproducing unit; 110 a recording apparatus; 111 a recording unit; 112 a copy control signal detecting unit; 113 a recording medium for recording; 121 a read signal from the recording medium 101; 122 a reproduction signal which is supplied from the reproducing apparatus 100 to the recording apparatus 110; 123 a copy control signal; and 124 a write signal to the recording medium 113.
In the reproducing apparatus 100 constructed by the recording medium 101 for reproduction and the reproducing unit 102 in FIG. 1, a recording signal is read out from the recording medium 101 by the reproducing unit 102 and is outputted as a digital or analog reproduction signal 122. On the other hand, in the recording apparatus 110 constructed by the recording unit 111, copy control signal detecting unit 112, and recording medium 113 for recording, the copy control signal detecting unit 112 detects the copy control signal 123. In accordance with the detection result, the recording unit 111 generates the write signal 124 which inhibits or permits the recording to the recording medium 113 for recording.
The recording apparatus for recording a signal to the recording medium 101 which is reproduced by the reproducing apparatus 100 will now be described. FIG. 2 is a block diagram of the recording apparatus by a digital signal. In FIG. 2, reference numeral 200 denotes an analog unit; 201 an information source from which information to be recorded is generated; and 210 a digital unit. The digital unit 210 comprises: an encoding unit 211, a copy prevention code generator 212, a synthesizer 213, a writing unit 214, and a recording medium 215. An analog information signal 231 is converted to a digital information signal 232 by an ADC (analog/digital converter) 221 and is supplied to the digital unit 210. In the digital unit 210, the encoding unit 211 encodes the digital information signal and supplies an information code 233 to the synthesizer 213. The synthesizer 213 synthesizes the information code 233 and a copy prevention code 234 from the copy prevention code generator 212. An output signal 235 from the synthesizer 213 is supplied to the writing unit 214 and an output signal 236 of the writing unit 214 is recorded in the recording medium 215. The information code 233 and copy prevention code 234 are recorded in the recording medium 215. The system of FIG. 2 can be applied to, for example, a mastering of a read-only disk medium.
FIG. 3 shows another example of a recording apparatus for digitally recording. According to the example of FIG. 3, the copy prevention code is added in the encoding unit 211. The information code 233 from the encoding unit 211 is supplied to a code reading unit 216 and an added copy prevention code 237 is separated. The copy prevention code is supplied to a control unit 217 of the copy prevention code. The control unit 217 limits a generation of copy. For example, when the copy prevention code is a code for permitting a copy of one generation, the control unit 217 generates a control signal 238 for rewriting the copy prevention code to a code for inhibiting the copy and a control signal 239 for instructing permission or inhibition of the recording of a signal to the recording medium 215 by the writing unit 214. When the original copy prevention code permits the copy of one generation, the control signal 238 is supplied to a code changing unit 218, the copy prevention code is changed to a code having the contents of inhibiting the copy, and the writing is permitted by the control signal 239. The system of FIG. 3 can be applied to, for example, a digital VTR.
In a copy system using a digital medium, the operation in case of a digital connection and the operation in case of an analog connection are different. Examples in those cases will now be described, respectively. First, the digital connection will be described. FIG. 4 is a schematic diagram of a copy system by the digital connection. Reference numeral 301 denotes a digital data reproducing apparatus; 302 a digital data recording apparatus; and 311 a digital signal. As for the operation of FIG. 4, the digital signal 311 is supplied from the digital data reproducing apparatus 301 to the digital data recording apparatus 302 and the recording operation of the digital data recording apparatus 302 is controlled by the copy control signal included in the digital signal 311.
FIG. 5 shows an example of the copy system by the digital connection. In FIG. 5, reference numeral 400 denotes a reproducing apparatus; 401 a recording medium on the reproduction side; 402 a reading unit; 410 a digital interface; 411 a communication path; 420 a recording apparatus; 424 a copy prevention code reading unit; 425 a copy control signal control unit; 426 a code changing unit; 421 a writing unit; 423 a recording side recording medium; 431 a read signal; 432 a digital reproduction signal; 435 a copy prevention code which was read; 436 and 437 control signals; and 438 a write signal.
The operation of the construction of FIG. 5 will now be described. In the reproducing apparatus 400 comprising the recording medium 401 for reproduction and reading unit 402, the read signal 431 obtained from the recording medium 401 is supplied to the reading unit 402 and is outputted as a digital reproduction signal 432. The digital reproduction signal 432 passes through the communication path 411 of the digital interface 410 and is supplied to the code reading unit 424 and the copy prevention code 435 is separated. The copy control signal control unit 425 decodes the separated copy prevention code 433 and reads the information. The control signal 436 for changing the copy prevention code is outputted to the code changing unit 426 and the control signal 437 for instructing the permission or inhibition of the recording of the signal to the recording medium 423 is outputted to the writing unit 421. In the construction of FIG. 5, not only the permission and inhibition of the recording but also the limitation of the copy about the generation can be performed.
The copy system by the analog connection will now be described. FIG. 6 shows a schematic construction. Reference numeral 501 denotes a digital data reproducing apparatus; 502 a digital data recording apparatus; and 511 an analog signal transmitted between the apparatuses 501 and 502. In the construction of FIG. 6, the analog signal 511 which was D/A converted and outputted from the digital data reproducing apparatus 501 is inputted to the digital data recording apparatus 502 and is A/D converted and digitally recorded. In such a system, when the copy control signal has been extinguished in the analog signal 511, the copy prevention control cannot be executed in the digital data recording apparatus 502.
A few methods have been proposed as a method of preventing the copy by an analog interface. For example, when the analog signal is a video signal, a phase of a color burst of an analog video signal to be outputted is partially inverted or a pseudo synchronization signal having an extremely large level is inserted as a sync signal for AGC, so that even if the normal reproduction can be performed. When the video signal is recorded by the VTR, a normal reproduction image is not obtained in a monitor receiver.
In a conventional copy system, a digital copy prevention code is added to a signal in which an information source was digitally encoded. In case of a digital interface, therefore, the digital recording apparatus detects the copy control signal and can execute the copy prevention control. Even if the digital data reproducing apparatus is used, however, in case of an analog interface, the digital signal as a copy control signal added by the D/A conversion is dropped out. The copy control signal cannot be consequently detected in the digital recording apparatus in which the signal is finally recorded. The copy prevention control cannot be performed. Thus, it is necessary to prevent the copy by using the difference between the AGC methods of the VTR and the monitor receiver or the difference between the characteristics of the APC methods.
As mentioned above, when executing the copy prevention by using the difference between the AGC methods of the VTR and the monitor receiver or the difference between the APC characteristics, there is a fear of occurrence of problems such that the copy cannot be prevented, a reproduction image of the monitor receiver is disturbed by a countermeasure for the copy prevention, or the like.